Protractor.



J. G. SPOPFORD.

PRoTnAo'roR.

APPLICATION FILED PEB. 14, 190 8.

Patented June 29, 1909.

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PROTRAGTOR. APPLIOATIDN FILED rm.14.1noa.

926,61 5 Patented June 29. 1909.

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Gitans, SI

UNTE STATES PATENT PROTRACTOR.

Specification of Letters Patent.

Patented YTune 29, 1909.

Application filed February 14, 1908. Serial No. 415,964.

To all whom fit may concern:

Be it known that 1, Jenson Gente Sror- FORD, a citizen el the United. States, residing at Hopedale, in the county ot' 'Voreester, State ol' Massachusetts, have invented eertain new and useful improvements in Protraetors, and I do here )y deelare the lfollewing to be a full, ele-ar, and exaet description oll the invention, suoli as will enable others skilled in the art to which it appertains to make and use the same.

rThis invention has relation to a new and uset'ul improvement in pretraeters.

The object et my invention is to provide a draltsmans protraeter adapted to be used in Connection with an ordinary T-square and that will enable the user te adjust the blade to any angle required.

ln the accompanying drawings l have shown in Figure 1 a faee view ol the pro tractor embodying my invention. YF 2 discloses a detached detail of the L-shaped member as used in my invention. Fig. 2% shows a face view of the bottom plate. Fig. 4 shows an enlarged central sectional view with portions broken away on the lint` 1 4 ot Fig. 1. Fig. 5 shows an edge view ol the blade, and Fig. 6, an end view of the protractor.

rlie improved device comprises two plates 2 6 having two of their edges (L l/ at right angles to eaeh other with the remainder of the plates segmental as at t with the (renter ol the segmental portion spaeed trom the edges e l/ of the plates and with an aperture 5 in the plate 2 and a. Corresponding aperture S in the plate 6, the two apertures being in alinement, as indicated. The plate 2 is lornied with a slot 4 curved eoneentrie to the apertures 5 8. The plates 2 6 are united at their right angled edges by an L shaped member 1, the L shaped member thus spaeing the plates apart and being seeured between them by rivets er other suitable fastening means. By this means the segmental edges ol the plates are spaced apart while the right angled edges ot the plates are closed by the L shaped member B.

Extending through the apertures 5 8 is a pin 9 having an annular central llange 14, the ends et the pin extending through the apertures and the llange extending between the plates 2 6, the l'lange thus forming shoulders upon which the plates bear, and likewise providing a central bearing between the plates larger than the apertures. upon this enlarged central portion 1l is a blade 1 1 ha ving an aperture 1() corresponding to and engaging the enlarged or llanged portion 14 ol the pin t), the blade thus having a relatively large bearing between the plates. rlhe outer portion ol' the blade is thieler than thel portion between the plates as at 1.2 whereby shoulders are formed which engage tho outer or segmental edges ot the plates, as at 123 14 in VFig. 5. '.l'he portion 11 ol the blade is provided with a. threaded aperture opposite the slot #1 and engaging this aperture is a threaded clamp serew 15 having a shoulder 17 and a milled head 16 whereby the screw may be operated and elamp the three parts 2 6 11 Vfirmly together when required. 'lhe shoulders 13 14 thus provide tor a bearing against the segmental outer edges ol' the plates 2 6 and the upper and lower surfaces ot the blade 12 come llush with the upper and lower surl'ares ol the plates, as saown in Figs. 4 and 6.

vWhen the implement is in use one ol the sides (Il l/ will be disposed upon a suitable rule or straight edge, preferably the blade A ot a T square, as shown.

Formed upon the plate 2 between the slot 4t and the segmental edge ol the blade are grznluations representing degrees olE a oirele from zero to ninety while upon the blade 12 is a vernier zr, to assist in setting the blade to the required angle.

The plat-e (i is lormed with numerous radial lines emanating troni the renter oll the aperture 8 and the taee otl the plate is again divided by a plurality ol' segmental lines whieh divide the radial lines into seetions, the spaces between the radial lines and the feg* mental lines having the values ol' sines, rosines and tangents l'or every Alive degrees, the radial lines cooperating with the degree lines on the laee elthe opposite plate. By this simple means it is obvious that the bladeI 11 may be set at any required angle.

The improved implement will be employed, as above slated, in eonneetion with a stra-ight edge, preferably with the blade ol' a T square as shown, and by its use any required. angle may be transferred to the paper on a drawing board by simply loosening the screw 16 and moving the blade to the required extent.

'.llie plate 6 and the lower l'aeo ol the blade 12 coming llush with eaeh other lie lat upon Swinging Y and tlius facilitate tlie operation, and remove very largely tlie element of uncertainty to tlie action of the device.

The device is simple in construction, can be inexpensively manufactured, and Will be found very useful for dralftsmen and engineers in laying out Worli, or in transferring to paper the routes made by the surveyors, and for other like purposes.

The plates 2 6 and tlie L shaped member' l Will preferably be of metal and may be plated or otherwise ornamented and protected, unile tlie blade lll may be of Wood, metal, or other material as may be preferred.

l. A device of the class described comprising a head portion consisting et a member formed el two rigid arms extending at riglit angles to eacli other, two plates connected at tlie opposite sides of said bars and provided Witli graduations, and Witli transversely alined bearing apertures therethrough in advance of said member, tlie free edges el tlie plates being segments of circles of which tlie centers el the apertures forni the center, one of tlie plates having a slot concentric to tlie segmental edge or" the blade, a pin extending in said bearings, a blade with the outer pertion equal in thickness to tlie combined thickness of tlie plates and said member and with a reduced portion extending between the paper,

said plates and swinging upon said pin, and clamping means operating througli said segmental slet.

2. A device of tlie class described comprisin@ a head portion consisting of a member formed of two rigid arms extending at right angles to eaeli otlier, two plates connected at tlie opposite sides ot' said bars and provided With graduations, and with transversely alined bearing apertures tlieretlirougli in advance of said member', the free edges er" the plates being segments of a circle of which the apertures form tlie center', of tlie plates 1naving a slot concentric to the segmental edge of the plate, a pin extending in said bearings, a blade witli tlie outer portion equal in thickness to tlie combined thickness of tlie plates and said member and Witli the reduced portion extending between said plates and swinging upon said pin, the reduced portions forming concaved shoulders bearing closely upon tie curved outer edges el tlie plates, a Vernier upon said blade coacting with the graduatiens on tlie plate, and clamping means operating through said segmental slot.

ln testimony whereof, l affix my signature, in presence or' two Witnesses.

JUDSGN GOULD SGFFORD.

Vllitnesses FRANK H. FRENCH, JOHN L. AnAMs. 

